Make callers of CommandLine use it via the base:: namespace.

chrome/browser/ui/views/ash/tab_scrubber_browsertest.cc

Index: chrome/browser/ui/views/ash/tab_scrubber_browsertest.cc
diff --git a/chrome/browser/ui/views/ash/tab_scrubber_browsertest.cc b/chrome/browser/ui/views/ash/tab_scrubber_browsertest.cc
index 0b06a156cde06a95ef609895c04993725bcea098..2290bd8445b7ab2208640a6acf0b10f75d20d52a 100644
--- a/chrome/browser/ui/views/ash/tab_scrubber_browsertest.cc
+++ b/chrome/browser/ui/views/ash/tab_scrubber_browsertest.cc
@@ -38,7 +38,7 @@ class TabScrubberTest : public InProcessBrowserTest,
       : target_index_(-1) {
   }
 
-  void SetUpCommandLine(CommandLine* command_line) override {
+  void SetUpCommandLine(base::CommandLine* command_line) override {
 #if defined(OS_CHROMEOS)
     command_line->AppendSwitch(chromeos::switches::kNaturalScrollDefault);
 #endif